Lithium-ion batteries (LIBs) have been developed as a promising power source for electric vehicles because of their high energy density and long lifetime. Graphite is widely used as an anode electrode material in the state-of-the-art LIBs. However, a graphite anode is usually only compatible with an ethylene carbonate (EC)-based electrolyte. When contacting with a propylene carbonate (PC)-based electrolyte, which is advantageous over the EC-based one because PC has a wider operating temperature range and higher low-temperature conductivity, the graphite anode may suffer from a substantial exfoliation problem during the initial lithium intercalation step.
Consequently, a PC-based electrolyte cannot be used in LIBs with graphite as the anode unless solid electrolyte interphase (SEI) film-formation additives are introduced into the electrolyte compositions in certain amounts. The SEI film-formation additives are usually reduced predominantly on the graphite electrode surfaces before PC is reduced. These additives mainly include some functional groups such as vinylene or cyclic unsaturated group. For example, vinylene carbonate (VC), vinyl ethylene carbonate (VEC) and fluoroethylene carbonate (FEC) have been widely studied and used as SEI film-formation additives for PC-based electrolyte compositions. They play an important role in the protection of the structure of the graphitic anode from destruction by PC. In addition, for some functional electrolyte systems, e.g., flame-retarded electrolytes or ionic liquid-based electrolytes, SEI film-formation additives also are needed. However, these additives tend to build up a thick SEI protective layer, which could significantly reduce the rate capability, low-temperature performance and cycling stability at elevated temperatures because of the high additional impedance and poor thermal stability from the SEI film.